In recent years, a device has become popular that handles image information digitally and for the purpose of highly efficiently transmitting and accumulating pieces of information, compresses and encodes an image by employing an encoding method that compresses the image through the motion compensation and orthogonal transform such as discrete cosine transform by using the redundancy unique to the image information. This encoding method includes, for example, MPEG (Moving Picture Experts Group) and H.264 and MPEG-4 Part 10 (Advanced Video Coding, hereinafter referred to as H.264/AVC).
Recently, for the purpose of further improving the encoding efficiency over H.264/AVC, JCTVC (Joint Collaboration Team-Video Coding) as the ITU-T and ISO/IEC joint standardization group has advanced the standardization of the encoding method called HEVC (High Efficiency Video Coding) (for example, see Non-Patent Document 1).
In the current draft of HEVC, a deblocking filter is employed as one of in-loop filters. As the deblocking filters, a strong filter and a weak filter are given; which one is employed is determined by using a filter determination formula for the block boundary.
In other words, whether to apply the strong filter or not is determined using the determination formula of the strong filter and for the block boundary where it has been determined that the strong filter is not applied, whether to apply the weak filter or not is determined using the determination formula of the weak filter.